picoCTF Solutions
picoCTF 2026General SkillsMedium

bytemancy 0

Published: March 20, 2026

Description

Can you conjure the right bytes? Download `app.py` and recover the exact input the server expects.

Setup

Download app.py

Download and read app.py to understand what byte sequence the server expects.

Launch the challenge instance and connect via netcat.

cat app.py

Solution

  1. Step 1Read the source code
    Download app.py. It prints a banner telling you exactly what to send: ASCII DECIMAL 101, three times, side-by-side, no space. ASCII 101 is the letter 'e'.
    cat app.py
  2. Step 2Send the payload
    The server checks that your input equals '\x65\x65\x65' (i.e. 'eee'). Just type or echo 'eee' and it returns the flag.
    echo 'eee' | nc <HOST> <PORT_FROM_INSTANCE>
    python3 -c "print('eee')" | nc <HOST> <PORT_FROM_INSTANCE>

Flag

picoCTF{byt3m4ncy_0_...}

app.py asks for ASCII decimal 101 × 3, no spaces. ASCII 101 = 'e', so send the three-character string 'eee'.